1. Field of the Invention
The present invention relates to a sheet supplying apparatus for separating and supplying sheets one by one to an image forming portion regarding originals set in an original reading apparatus.
The sheet may be a cut sheet such as a transfer sheet, photosensitive sheet, a heat-sensitive sheet, an electrostatic recording sheet, a print sheet, an original, a card or an envelope supplied to an office equipment or other sheet using apparatus such as a copying machine, a printer, a printing apparatus, a facsimile and the like. The sheet is not limited to a paper sheet.
2. Related Background Art
Conventional control effected in a copying operation for copying an original in a copying machine using an electrophotographic apparatus will now be explained with reference to FIGS. 13 and 14.
When originals are set at a reading portion by an operator and a copy start button is depressed, a recording motor Ml is driven on the basis of a signal from a CPU provided on a DC controller base plate. After a predetermined time period is elapsed, when a signal for effecting the supplying of a recording sheet is transmitted from the CPU to a recording portion, sheet supply clutches (CL1, CL4) are turned ON to rotate a sheet supply roller 206, thereby supplying the recording sheet from a sheet supply portion. Thereafter, sheet supply roller release solenoids (SL1, SL2) are turned ON to separate the sheet supply roller 206 from the recording sheet.
The fed recording sheets are separated one by one by a convey roller 207 and a separation roller 208, and the separated recording sheet is sent to a convey path. When a predetermined time period is elapsed after the sheet supply clutches (CL1, CL4) are turned ON, vertical path roller drive clutches (CL2, CL3) are turned ON, with the result that the recording sheet is conveyed by vertical path rollers 209 set to permit conveyance of a small size sheet. Even after the recording sheet reaches the vertical path rollers (next stage convey means) 209, since the sheet supply clutches (CL1, CL4) are still being turned ON, the separation roller 208 is rotated in the same direction as the convey roller 207, thereby preventing recording sheets other than an uppermost recording sheet from entering into a nip between the convey roller 207 and the separation roller 208.
When a predetermined time period is elapsed after the vertical path roller drive clutches (CL2, CL3) are turned ON, a pre-regist roller drive clutch (CL9) is turned ON, with the result that the recording sheet is sent to a pair of regist rollers 211 by a pair of rotating pre-regist rollers 210. A sensor (not shown) is disposed in front of the pair of pre-regist rollers 210 so that, if the recording sheet does not reach the sensor within a predetermined time period, it is judged that a jam condition occurs. When a predetermined time period is elapsed after the recording sheet reaches the pair of pre-regist rollers 210, the sheet supply clutches (CL1, CL4) are turned OFF.
The recording sheet conveyed to the regist rollers 211 abut against a nip of the regist rollers 211 (which are now stopped since a regist roller drive clutch (CL8) is turned OFF), thereby forming a loop in the sheet to correct the skew-feed of the recording sheet. Thereafter, the recording sheet is held by the regist rollers 211. A motor of an optical system starts to be driven by ON/OFF of the regist rollers 211, so that the original is exposed by an original exposure lamp 212 and light reflected from the original is illuminated onto a CCD portion 214 through mirrors 213. By controlling ON/OFF of a laser 215 on the basis of the image information of the original read by the CCD portion 214, a dot pattern image is formed on a photosensitive drum 216. The electrostatic latent image formed on the photosensitive drum 216 is visualized by a developing portion 217 of the recording portion with toner as a toner image.
The regist rollers are driven so that an image tip end of the toner image formed on the photosensitive drum 216 coincides with a tip end of the recording sheet, and the image on the photosensitive drum 216 is transferred onto the recording sheet by a transfer charger 218. The toner image rested on the recording sheet is conveyed to a fixing portion 220 by a convey portion 219 without applying vibration to the recording sheet. In the fixing portion, heat and pressure are applied to the recording sheet, thereby fixing the toner image to the sheet as a permanent image. The recording sheet on which the image information was copied is discharged onto a discharge tray (removably attached to the copying machine) through a discharge portion 221.
In the above-mentioned conventional technique, it is required to continuously apply electric power to the electromagnetic clutches, thereby increasing the power consumption. Further, since the retard roller is rotated for a long time, the durability is worsened due to wear and the like. The sensors and the like are required to detect the position of the recording sheet in order to control the electromagnetic clutches, thereby making the construction complicated. Further, since the electromagnetic clutches must be controlled on the basis of signals from the sensors, the control becomes complicated.